614 / 2024-09-18 16:27:10

Climate impacts of the Atlantic Multidecadal Variability in pacemaker experiments

Atlantic Multidecadal Variability,decadal climate changes,numerical experiment

Session 20 - Decadal Climate Variability: Key Processes of Air-Sea Interaction, Mechanisms and Predictability

Atlantic Multidecadal Variability (AMV) significantly influences regional and global climate, as evidenced by observations and climate model simulations. While previous studies primarily utilized atmosphere-only models or coupled simulations with fixed AMV patterns, this research employs pacemaker experiments using time-varying observational North Atlantic sea surface temperature (NASST) records. By analyzing high-pass data, we demonstrate that AMV's global impact stems mainly from its tropical component, with ten ensemble members sufficiently distinguishing forced signals from internal variability. The response to a warm AMV anomaly unfolds in four stages: (1) warm pool warming and Indo-Western Pacific easterly anomalies driven by tropical Atlantic diabatic heating, (2) eastward propagation of equatorial thermocline anomalies, leading to La Niña-like conditions in the eastern Pacific after 7-10 months, (3) persistent La Niña conditions for 11-20 months via Bjerknes feedback and Aleutian low weakening through tropical teleconnections, and (4) emergence of a negative Pacific Decadal Oscillation pattern in the North Pacific after 21-25 months. These findings underscore the importance of incorporating time-varying SST observations in pacemaker experiments to fully capture complex inter-basin interactions.